Internal combustion engine with a positive displacement supercharger mechanically driven from the engine crankshaft

ABSTRACT

A piston-type internal combustion engine is fitted with a mechanically driven displacement supercharger such that the displacement volume of a supercharging chamber for compression of the combustion air is made equal to the maximum requirement of an engine cylinder to be filled. The stroke rate of the supercharger is equal to the ignition rate of the engine and the piston motion of the supercharger bears a given phase relation to the piston motion of the engine in line with the desired supercharging effect, such phase relation preferably being adjustable.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to an internal combustion piston engine with apositive displacement supercharger driven mechanically from the enginecrankshaft for compression of the engine combustion air.

Superchargers so far used for the supercharging of internal combustionpiston engines are inefficient and expensive to manufacture so that theyare so far not, in particular, suitable for small motor vehicle engines.Because of its satisfactory torque characteristic at low engines speeds,however, a mechanically driven displacement supercharger would seeminherently to be most suited for small private cars. The high costs ofmanufacture as noted, that more specially arise because it is hardlypossible to make the air flow match requirements as based on theoperating condition at a given time, and the high driving power that hasto be delivered by the crankshaft, have so far greatly limited the useof mechanically driven superchargers for small vehicles.

The object of the present invention is to so design an internalcombustion engine of the sort noted at the outset herein thatsupercharger operation is worthwhile even in small vehicles.

In order to realize this object in the case of such an internalcombustion engine as noted at the outset, the piston displacement of onesingle supercharger chamber is made to suit the maximum air requirementof one engine cylinder to be supercharged, the stroke rate of thesupercharging chamber or chambers of the supercharger is equal to theignition frequency of the engine and the phase of piston motion of thesupercharger bears a given relation to the piston motion of the enginein line with the desired supercharging effect.

The outcome of this is that it is then possible to supercharge with arelatively low power requirement, because the air from the superchargermay be displaced directly into the respective engine cylinder that is tobe filled so that no energy is needed for forcing out the air into astorage means or for forcing back the engine piston as the precompressedair flows into the engine cylinder.

In keeping with a useful development of the invention, an adjustablepressure controller, functioning as an air flow controller, is placed inthe connection between the supercharger and the engine cylinder that isto be supercharged.

As part of particularly beneficial form of the invention a device forchanging the phase relationship is placed in the driving connectionbetween the engine crankshaft and the supercharger as an air flowcontroller.

A still further useful development of the invention which economizes inpower is such that the piston displacement of one separate superchargerchamber is equivalent to the maximum amount of air desired in the enginecylinder to be filled less the amount of air drawn in by the enginepiston and the phase relationship of the piston motion of thesupercharger is so set in relation to the piston motion of the enginethat the supercharger forces the maximum desired amount of extra airinto the engine cylinder during the engine piston motion in the vicinityof bdc (bottom dead center).

It is furthermore possible as part of another development of theinvention for the air amount control to be automatically set by theoperational parameters of the overall system.

A more detailed account of the invention will now be given using theworking examples thereof to be seen in the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view of a cylinder to an internal combustionengine and of a mechanical supercharger fitted thereto.

FIG. 2 is a diagrammatic cross section through a supercharger of thesame design as in FIG. 1 on a larger scale.

FIG. 3 is a view looking in the direction of the arrow III in FIG. 2.

FIG. 4 shows a modified form of the construction of FIG. 3.

FIG. 5 is a diagrammatic view of a mechanically driven supercharger thatmay also be used as an expander for the air.

FIG. 6 is a diagrammatic section through a supercharger piston having aleakage vent for gas.

FIG. 7 is a view of a further form of supercharger with a balancingweight arrangement to balance inertia.

FIG. 8 is a diagram of conventional supercharger operation.

FIG. 9 is a diagram of theoretical, known belated supercharging.

FIG. 10 is a diagram of a first form of the method of the invention.

FIG. 11 is a diagram of a second form of the method of the invention.

FIG. 12 is a diagrammatic side view of a belt drive designed as amechanical link between the supercharger and the engine output shaft.

FIG. 13 shows a further form of this belt drive.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 it will be seen that the cylinder 10 of an engine has a movingpiston 12 in it and furthermore an inlet valve 14 and an outlet valve16. The inlet valve 14 is joined by a duct 18 with a check valve 20directly with the outside atmosphere and furthermore by way of a branchduct 22 there is a connection with the air outlet 24 of a positivedisplacement supercharger 26. The duct 18 may have means for shutting itoff between the check valve 20 and the branch duct 22.

The positive displacement supercharger 26 has a supercharging chamber28, in which a partition 30 is placed in the form of a moving flatpiston for the inducation of air through an air inlet 32, and todisplace the air out through the air outlet 24 into the engine cylinder10. The air inlet 32 and the air outlet 24 are fitted with check valves34 and 36. The partition 30 is joined to a guide rod 38, that ismovingly guided at a point outside the supercharger chamber 28 by aguide 40 in an axial direction so that the means for sealing and guidingthe partition 30 are separated from each other and for this reasonfriction is cut down to a minimum and there are furthermore favorableeffects as regards upkeep and lubrication.

The guide rod 38 is linked by way of a connecting rod 42 with a crank44, which is able to be driven by a belt drive 100 from the enginecrankshaft 46 as will be explained later.

FIG. 2 shows a similar form of the supercharger 26, in which casehowever the air inlet 24 and outlet 32 are placed on the side of thepartition 30 that is turned in the opposite direction to the guide rod38. In the case of this design of positive displacement supercharger thepartition 30 may be made very thin, because it is guided by the guiderod 38. On the other hand, with a short stroke, there is a large crosssection area for the inlet opening 24 and the outlet opening 32 to beplaced in, so that specially beneficial effects are produced onoperation of the supercharger.

FIG. 3 shows two possible forms of the cross section of these openings,in which respect on the left there is a plate valve in the form of anair outlet check valve 34 and on the right there is a semi-circular airinlet check valve 36, which may be in the form of a strip spring, forexample.

FIG. 4 shows a modification in the case of an oval air inlet crosssection, it furthermore being possible to get an optimum opening crosssection with round valves as well.

The significant useful effect produced by the mechanically drivendisplacement supercharger shown is that the mechanical connection withthe engine crankshaft 46 makes it possible for the stroke rate of thesupercharger chamber or chambers to be kept at a value equal to theignition rate or frequency of the engine, the mechanical connectionfurthermore making it readily possible to design for a phaserelationship between the motion of the partition 30 and the pistonmotion of the engine in line with the desired supercharging effect.Furthermore this phase relationship may simply be modified, if desired,as will now be explained on the basis of FIGS. 6 and 7. More specially,this system makes it very simple to regulate the air flow in keepingwith the instantaneous operating conditions.

FIG. 5 shows a supercharger 50 of the same design as that of FIG. 1, inwhich however the partition in the supercharger chamber 28 separates anupper exhaust gas chamber 54 from the lower air chamber 52, such upperchamber 54 having an exhaust gas inlet 56 and an exhaust gas outlet 58.Therefore the supercharger 50 may also be used as an expander, where theexhaust gas coming in via the exhaust gas inlet 56 from the enginecylinders performs work on the partition 30 when expanding, such workthen serving to assist in driving the engine crank shaft. In thisrespect the exhaust gas and the combustion air are only separated by thepartitions 30. To improve the sealing effect the outer edge face of thepartition 30 has a groove 60 with glands placed on the two sides thereofrunning round the outer limit of the partition 30. The groove 60 is, asmay be seen from FIG. 6, joined by a duct 62 running along inside theguide rod 38 with the outside atmosphere.

FIG. 7 shows one possible way of balancing the inertia of the partition30. To this end the guide rod 38 is designed with racks on both sides ofits section 70 which is at least as long as the stroke of the rod. Thesetwo racks 72 and 74 mesh with stationary pinions 76 and 78 respectively.There is a balancing or counter weight 80 that has an opening 82 for theguide 38 to move through, and it has two parallel racks 84 and 86meshing with the sides of the pinions 76 and 78 facing away from theguide rod 38, so that the balancing weight will always move in adirection opposite to that of the partition 30.

Using the mechanically driven supercharger described herein the enginecylinder 10 may be supplied directly with the air needed for a cycle,there being two modes of operation in this respect. It is on the onehand possible for combustion air to be taken in during the suctionstroke by the engine piston 12 while concurrently air is forced out ofthe supercharger, as for example the supercharger 26 in FIG. 1, into theengine cylinder 10 so that there is a concurrent operation of thesupercharger 26 with the suction stroke, for which reason this mode ofoperation may termed "concurrent supercharging". On the other handhowever it is possible for air firstly only to be drawn in by the piston12 and for such air to be followed only later near the bdc of the piston12 when the supercharger 26 supplies compressed air, such operationbeing termed "direct delayed supercharging".

To make possible a better understanding, an account will now be given of"concurrent supercharging" and the "direct delayed supercharging" usingFIGS. 8 to 11 to make a comparison with known methods. In each of thesegraphs the horizontal axis represents the displacement volume of thesupercharger chamber corresponding to the piston motion, the airrequirement in all the examples being 1.5 liters and the volume ofcombustion chamber to be filled being 1 liter, the desired compressionratio being therefore 1.5 to 1. Dead space in the system is neglected.The upright graph axis represents pressure, in which respect thepressure P1 is the atmospheric pressure and the pressure P2 is the finalsupercharging pressure in the engine cylinder. The position UT on thehorizontal axis represents bdc, i.e. the position of the positivedisplacement supercharger in which within its working cycle thesupercharging chamber has its greatest volume. OT marks the tdcposition, i.e. the position of the positive displacement supercharger inwhich the supercharging chamber has the minimum volume within itsworking cycle.

The graph of FIG. 8 represents motion and changes in pressure in thecase of conventional supercharging. In this case the combustion air isfirstly compressed from the atmospheric pressure P1 to the superchargingpressure P2 and then forced out of the positive displacementsupercharger into an intermediate storage device (air manifold ordistributor), whence the compressed air then flows into the enginecylinder. In the plot of the pressure changes it is assumed that thestorage means is infinitely large for simplification so that thepressure P2 is kept constant after the compression.

In FIG. 8 there is no direct relationship between the timing of thecompression stroke of the supercharger and the suction stroke of theengine piston, because the air will have reached its cylinder-fillingpressure any time before the suction stroke of the engine piston. Itwill be seen that there is a relatively small amount A1 of the work tobe performed, i.e. the compression work, and a relatively large amountA2, that represents the work needed to expel the compressed air out ofthe supercharger into the buffer formed by the intermediate storagemeans or air manifold, which will generally have a capacity of severaltimes the displacement of one engine cylinder or a supercharger chamberrespectively. In the supercharging operation in FIG. 8 the compressedair makes its way into the engine cylinder right from the start of theinduction stroke, i.e. as from the opening of the inlet valve. Althoughthe energy A2 is more or less completely recovered when the combustionair fills the engine cylinder and forces back the engine piston, thiswork A2 has to be furnished by the supercharger and because of theefficiency (depending on involved factors) of about 0.33 there is asubstantial loss in power and an increase in fuel consumption.

FIG. 9 shows operation of a theoretically known method in delayedsupercharging. In this case it is only the volume equal to thedifference between the desired air requirement and the volume of theengine cylinder to be supercharged that is compressed by the positivedisplacement supercharger. However this differential volume has to becompressed to a high pressure designated by P3 and it is expelled atthis high pressure into a storage means, the work of compression beingdenoted as A3 and the work of expulsion being denoted A4. The compressedair goes out of the storage means towards the end of the suction strokeafter the opening of a timing valve and passes into the engine cylinder.

But for the synchronization of the timing valve, no synchronizationbetween the motion of the positive displacement supercharger and thepiston of the engine cylinder to be filled is necessary or made possiblein the supercharging operation according to FIG. 8 or in the case ofconventional delayed supercharging as in FIG. 9. The useful effects ofthe invention stem from such synchronization that is so designed thatthe air displaced from the supercharger flow directly--without anyintermediate storage means--into the engine cylinder. FIGS. 10 and 11will show two different forms of this method of operation.

In the method illustrated in FIG. 10 the expulsion and compressionstroke of the positive displacement supercharger lasts for the wholeduration of the suction stroke of the engine piston. The combustion airis drawn in by the piston moving in the cylinder and concurrently withthis the air is expelled from the positive displacement supercharger,and because of the larger displacement of the supercharger, said air isat the same time compressed from the atmospheric pressure P1 to thefinal supercharging pressure P2, for which reason this form of themethod will be termed "concurrent supercharging". This effect may bemade even more pronounced by a "retarding" phase shift of thesupercharger piston.

In the case of such concurrent supercharging the air volume pumped bythe positive displacement supercharger is equal to the volume pumped inconventional supercharging as represented in FIG. 8, with the differencehowever that the supercharging pressure P2 is only reached at the end ofthe compression stroke of the positive displacement supercharger, thatis to say tdc, coinciding in time with the end of inlet into the enginecylinder in question. As will be seen from a comparison between FIGS. 8and 10, the amount of work performed is less. The saving in work ismarked E1.

FIG. 11 shows a method which represents a still further improvement, inwhich the air also flows directly out of the displacement superchargerinto the engine cylinder and in which the energy requirement is reducedstill further. In this method the engine piston firstly draws in air atatmospheric pressure without, for the moment, any combustion air fromthe displacement supercharger being compressed and expelled. It is onlywhen the piston in the engine cylinder is near bdc, i.e. shortly beforethe inlet is shut, the differential volume is propelled by thedisplacement supercharger directly into the engine cylinder in order tobring the drawn-in air that is still at atmospheric pressure up to thedesired charge pressure P2. Unlike theoretical known delayedsupercharging as in FIG. 9, the compression of the differential airvolume in this case is strictly timed in relation to the piston motionin the engine cylinder and forced directly out of the displacementsupercharger into the combustion chamber, for which reason thissupercharging method is to be termed "direct delayed supercharging".

As will be seen from a comparison between FIGS. 8 and 11 it is duringthe compression stroke in the case of direct delayed supercharging thatthe work marked A1 in FIG. 8 is performed, such work causing thepressure in the engine cylinder to go up to the final charging pressure.The saving in work as compared with conventional supercharging is markedas E2. In this method of operation the driving power needed for thesupercharging device is--as may be theoretically proved--about 18% ofthe driving power for conventional supercharging, in the case of whichthe combustion air is first compressed, expelled into a buffer and thenmakes its way into the cylinder.

For the "concurrent supercharging" and the "direct delayedsupercharging" methods described herein the synchronization of theengine piston and of the supercharging piston is important. As a resulta possibility is however opened up of controlling the air flow byshifting the phase relationship between the engine and the supercharger.This is more specially of value for controlling the air flow from amechanically driven supercharger, as is to be seen from example in FIG.1, because it is then no longer necessary to have a complex air flowcontrolling system by changing stroke or speed.

The supercharger 26 to be seen in FIG. 1 is driven by a belt drivegenerally referenced 100 from the engine crankshaft 46, the belt drive100 comprising a means to make it possible to change the phaserelationship between the engine crankshaft 46 and the crank 44 drivingthe supercharger 26. This means will be described in more detail inconnection with FIGS. 12 and 13.

With "direct delayed supercharging" the engine cyinder 10 (see FIG. 1)is completely filled, when the peak of the pressure increase produced bythe supercharger 26 is exactly synchronized with the shutting of theinlet valve 14 of the engine cylinder 10. If this timing is changed sothat the end of the pumping stroke of the supercharger is no longer atthe "optimum" point in time, at which the inlet valve closes, themaximum pressure P2 in the cylinder will not be reached and the degreeof filling will be less.

In this respect the supercharger may be advanced or retarded in relationto the motion of the engine piston 12. If the supercharger comes to theend of its pumping stroke before the inlet valve 14 shuts, the suctionby the engine piston 12 and the pumping of air by the supercharger 26will overlap to a greater degree and the overall amount of air drawn inby the piston in the engine cylinder 10 during the stroke willcorrespondingly be cut down. If the supercharger comes to the end of itspumping stroke after the closing of the inlet valve 14, it will nolonger be possible for the full pumped volume of the supercharger to getinto the engine cylinder and the degree of filling will again be less.However in this case in the final phase of the pumping stroke thesupercharger will firstly be performing useless work. The pressure builtup in the suction duct of the engine as a result may however be usefulafter the opening of the inlet valve 14 in order to scavenge the enginecylinder 10.

The belt drive 100 to be seen diagrammatically in FIG. 12 comprises abelt 110, preferably a toothed one, that runs over four pulleys in all,namely a driving pulley 114, a driven pulley 112 and two furtherpulleys, i.e. a pulley 120 placed against the belt run moving from thedriven pulley 112 to the drive pulley 114 and able to be moved in adirection normal to the direction of motion of the belt, and furthermorea pulley 122 that may be adjusted in a direction across the direction ofbelt motion. In other words, the pulley 120 is on the return run 116 ofthe belt 110 and the pulley 122 is on the driving run 118 of the belt110. This arrangement is an efficient one because the pulley 120 ispressed by a spring 124 against the belt 110 in order to keep up thedesired belt tension. If (in a case in which the pulley 120 were to runon the driving run of the belt) it were possible for the pulley 120 toflutter somewhat transversely in relation to the direction of the motionof the belt independently of any motion caused by an adjustment of thepulley 122, the engagement of the pulley 120 with the driving run wouldcause small uncontrolled changes in length of the driving run and forthis reason a departure from absolutely regular running of the drivingpulley 114 and of the driven pulley 112.

On the other hand the pulley 122 may be positively and definedlyadjusted in its position normal to the direction of running of the belt110, the pulley 122 is here mounted in a piston rod 126, that is joinedwith the piston 130 sliding in a piston 128, such piston being able tobe acted upon on both sides hydraulically, i.e. the cylinder 128 withthe piston 130 is a double acting hydraulic actuator which may be usedfor exact adjustment of the position of the pulley 122. Hydraulicoperation makes possible a simple regulation of the phase of the beltdrive as a function of externally ascertained parameters, for examplethe operating data of the motor vehicle and of its IC engine, when thebelt drive is used for valve operation of the engine in keeping with theexample noted in the introduction hereof.

If the pulley 122 in FIG. 8 is moved to the right, the driving belt run188 becomes longer, whereas the return run 116 is representativelyshortened so that the driven pulley is advanced in relation to thedriving pulley. If the pulley 122 is moved in the opposite direction,the driving belt run 118 will gradually move into its shortest,straightened position, which is preferably such as to represent a retardof the driven pulley 122 in relation to the driving pulley 114, whereasthe phase shift of zero should be roughly in the middle between the twopositions of the pulley 122 if the possibility of an advance and of aretard is desired. The arrangement is such, in the case of both workingexamples, that in the one end position of the adjustable pulley 122 theone belt run 116 or 118 runs in a straightened condition and therespective other belt run 118 or 116 will then have its maximumdeflection out of the straightened position. Keeping to this stipulationvariations in the placing of the pulleys 120 and 122 are possible. Forexample, in FIG. 12 the pulley 120 might be placed on the other side ofthe belt, although then the belt run 116 would have to be pressedthereby not to the left but to the right out of the straightenedposition. In the arrangement of FIG. 12 the spring 124 has to compensatethe adjustment motion of the pulley 122. In the case of the workingexample of FIG. 13 this is not necessary so that in this case one mayhave a smaller, stiffer spring.

In the working example of FIG. 13 the piston rod 126 is joined to abearing element 132, on which the pulley 122 is bearinged so that themotion of the pulley is limited to a rotary one. The pulley 120 issupported in a slide 134, that may be shifted to a limited degree in thebearing element 132 transversely in relation to the direction of thebelt 110, to which end there may be guide slots 136 for mounting theslide 134. The slide 134 is loaded in the bearing element 132 by way ofa spring 138. This spring functions generally to keep up the tension ofthe belt 110 at the desired level.

If the piston 130 is moved, the pulleys 120 and 122 are moved as well.Since the two pulleys 120 and 122 contact with the same face of the belt110, the one belt run 116 is lengthened by roughly the same amount asthe amount by which the other belt run 118 is shortened and the otherway round. Slight departures, that occur on leaving the symmetricalposition of the two lengths 116 and 118, may be allowed for by thespring 138.

The manner of operation would be the same if the two pulleys 120 and 122were to be placed on opposite respective sides of the belt, it onlybeing necessary in this case to adopt the arrangement as described atthe end of the account of FIG. 2. If one keeps to this condition, i.e.that in the one end position the one belt run is straightened and theother is deflected to the maximum degree, it would be possible, gettingthe same useful effects as regards the size of the spring 138, for thepulley 120 also to be mounted with the help of the slide 134 in abearing element which would be driven in the opposite direction to thepiston rod 126 and the pulley 122 bearing thereon, even although thisarrangement would seem to be of lesser utility because of the morecomplex mechanical design. However it will be clear that the teaching ofthe invention may be put into practice in a number of very differentways and is not limited to the examples explained herein.

To be able to adjust the belt tension, it is preferred that the force ofthe spring 124 or 138 be adjustable, as is known in connection with beltdrives.

In place of the crank drive 100 described above and shown in the drawingit would be possible to use other means for the transmission of powermechanically or hydraulically for example, inasfar as they make itpossible for the phase relationship between the driven and drive membersto be varied.

For the "direct delayed supercharging" of multicylinder engines it is ofadvantage for the supercharger to be driven at a speed of twice that ofthe crankshaft and for the number of the supercharging chambers to behalf as large as the number of engine cylinders in order to make theexpulsion phase of the supercharger shorter than the induction stroke ofthe engine.

What is claimed is:
 1. A positive displacement supercharger adapted foruse with an internal combustion engine, comprising:said superchargerhaving a chamber with an internally moving piston, wherein thedisplacement of said supercharger piston in said chamber is related tothe maximum air requirement of one of the cylinders of said engine, ductmeans for conducting pressurized air from said supercharger to saidengine including a branch duct which permits said engine to drawatmospheric air by suction, a mechanical drive for driving saidsupercharger in a timed relationship with said engine such that themotion of the pistons of said engine and said supercharger have a phaserelationship such that pressurized air is supplied by said superchargerto said engine cylinder at a point in the operating cycle of said enginewhere the engine piston is near its bottom dead center position, checkvalve means coupled with said branch duct enabling atmospheric air to bedrawn through said branch duct during one portion of the suction strokeof said engine cylinder and pressurized air is provided by saidsupercharger during another portion of said suction stroke.
 2. Thepositive displacement supercharger according to claim 1 wherein saidmechanical drive is capable of varying the phase relationship betweensaid movements of said engine piston and said supercharger piston. 3.The positive displacement supercharger according to claim 1 wherein saidbranch duct further comprises a one-way check valve which permitsatmospheric air flow only toward said engine cylinder.
 4. The positivedisplacement supercharger to claim 2 wherein said mechanical drivecomprises a crankshaft of said engine, a belt which engages a drivingpulley connected to said crankshaft of said engine, a crankshaft of saidsupercharger, said crankshaft of said supercharger having a drivenpulley connected to said crankshaft of said supercharger, said beltengages said driven pulley such that said belt defines a driving runbetween said pulleys on one side of said pulleys, and defines a slackrun between said pulleys on another side of said pulley said drivefurther including one or more adjusting rollers acting on both saiddriving and slack runs for changing the length of said runs, therebychanging the phase relationship between said engine crankshaft and saidsupercharger crankshaft.
 5. The positive displacement superchargeraccording to claim 1 wherein the speed of rotation of said superchargeris some multiple of the speed of rotation of said engine wherein saidsupercharger supplies air to a number of said engine cylinders equal tosaid multiple.